采用在双体单自由度结构间设立K e lv in型被动控制单元的最优参数表达式,并基于等效双体单自由度体系求得了相邻多层剪切型结构间控制器最优参数。利用列举法并基于二次型性能指标值(LQR)确定了控制器优化布置位置,讨论了布置控制器后对结构地震响应的影响以及对结构动力特性的影响,通过数值分析证实了采用等效双体单自由度体系代替相邻多自由度结构体系的正确性,表明了这种被动控制方法能够非常有效地减小在地震作用下相邻结构的地震响应。
Top-down crack in asphalt pavements has been reported as a widespread mode of failure.A solid understanding of the mechanisms of crack growth is essential to predict pavement performance in the context of thickness design,as well as in the design and optimization of mixtures.Using the coupled element free Galerkin (EFG) and finite element (FE) method,top-down crack propagation in asphalt pavements is numerically simulated on the basis of fracture mechanics.A parametric study is conducted to isolate the effects of overlay thickness and stiffness,base thickness and stiffness on top-down crack propagation in asphalt pavements.The results show that longitudinal wheel loads are disadvantageous to top-down crack because it increases the compound stress intensity factor (SIF) at the tip of top-down crack and shortens the crack path,and thus the fatigue life descends.The SIF experiences a process "sharply ascending—slowly descending—slowly ascending—sharply ascending again" with the crack propagating.The thicker the overlay or the base,the lower the SIF; the greater the overlay stiffness,the higher the SIF.The crack path is hardly affected by stiffness of the overlay and base.
Base isolation is one of the most promising alternatives among the structure control methods. In recent decades, base isolation has been seriously considered for civil structures, such as buildings and bridges, subjected to ground motion. The research achievements and development of seismic base isolation technique for civil structures in Huazhong University of Science and Technology (HUST) are introduced. The achievements include project applications, experimental research results and theoretical innovation.
